Tube fitting and assembly method

ABSTRACT

A tube and fitting assembly for pressurized fluids is provided which may provide a fluid-tight seal up to the bursting pressure of the tube at relatively high temperatures. The tube and fitting assembly includes a malleable tube and a fitting having a first portion forming an external surface, a second portion radially larger than the first portion to form an abutment facing the first portion, and a recess formed within the abutment and facing the first portion. A gasket formed of a high temperature material is provided in the recess. An end of the tube is radially inwardly compressed on the external surface of the fitting and extends into the recess to the gasket. The tube is assembled to the fitting by placing the tube over the first portion of the fitting and the external surface and gripping the tube with jaws having an inward nose projection of a small axial extent at about the forward end of the fitting. The fitting and the tube are longitudinally moved relative to the jaws to longitudinally compress the tube ahead of the nose projection to deform the tube radially inward against the fitting. A portion of the tube is extended into the recess to form a seal between the tube and the fitting by expanding the tube longitudinally into the recess during the step of relative longitudinal movement or by inserting the tube longitudinally into the recess during the step of placing the tube over the first portion of the fitting. Also disclosed are variants of the assembly and method having auxiliary seal members and sleeves used in cooperation with very thin wall tubes.

This is a divisional of application Ser. No. 08/635,024, filed Apr. 19,1996 which is a continuation-in-part of Ser. No. 08/445,282, filed May19, 1995 now abandoned which is a divisional of U.S. Ser. No. 233846filed Apr. 26, 1994, now U.S. Pat. No. 5,544,406, issued Aug. 13, 1996.

BACKGROUND OF THE INVENTION

Tube and fitting assemblies have been devised in many differentstructures and methods of assembly. The usual case of a tube telescopedover a part of a fitting is where jaws of kind have generally radiallycompressed the tube into sealing contact with that part of thetelescoped tubing and fitting. In such a case, the tube is compressedradially inward to make the seal. This is difficult to actually make agood seal because the tube, even though malleable and deformed past itselastic limit, tends to have a certain amount of elasticity and springsback radially outwardly after the jaw pressure has been removed. Thus,in many cases the fluid-tight seal between the tube and the fitting isdestroyed or at least lowered as to the fluid pressure it willwithstand. Additionally, at high temperatures the tube and/or fittingmay relax. Thus, in many cases the fluid-tight seal between the tube andfitting is destroyed or at least lowered as to the temperature it willwithstand.

SUMMARY OF THE INVENTION

The present invention provides a tube and fitting assembly and method ofassembly wherein the radial expansion does not occur after the assemblypressure is removed and the assembly jaws longitudinally move relativeto the tube to give compression thereof. This longitudinal relativemovement causes the tube to bulge outwardly and bulge inwardly in frontof the jaws during relative movement so that if there is any relaxationof the tube when the pressure is removed this relaxation is radiallyinwardly instead of outwardly. This assures a fluid-tight seal whichwithstands pressure up to the bursting pressure of the tube atrelatively high temperatures.

Accordingly, the tube and fitting assembly of the present inventionincludes a malleable tube and a fitting having a first portion formingan external surface, a second portion radially larger than the firstportion to form an abutment facing the first portion, and a recessformed within the abutment and facing the first portion. An end of thetube is radially inwardly compressed on the external surface of thefitting and extends into the recess of the fitting to make a fluid-tightseal between the tube and the fitting which withstands a fluid pressurewithin the tube. Preferably, a seal member is provided within therecess. A method of assembly of the present invention includes placingthe tube over the first portion of the fitting and the external surfaceand gripping the tube with jaws having an inward nose projection of asmall axial extent at about the forward end of the fitting. The fittingand the tube are longitudinally moved relative to the jaws tolongitudinally compress the tube ahead of the nose projection to deformthe tube radially inward against the fitting. A portion of the tube isextended into the recess to form a seal between the tube and thefitting. Preferably the tube is extended into the recess either byexpanding the tube longitudinally into the recess during the step ofrelative longitudinal movement or by inserting the tube longitudinallyinto the recess during the step of placing the tube over the firstportion of the fitting.

BRIEF DESCRIPTION OF THE DRAWINGS

These and further features of the present invention will be apparentwith reference to the following description and drawings, wherein:

FIG. 1 is a longitudinal view, in cross-section of a tube and fittingready for assembly;

FIG. 2 is a longitudinal view, in cross-section, of the tube and fittingof FIG. 1 as assembly is beginning;

FIG. 3 is a is a longitudinal view, in cross-section, of the tube andfitting of FIG. 2 as assembly is partly completed;

FIG. 4 is a longitudinal view, in cross-section, of the tube and fittingof FIG. 3 as assembly is completed;

FIG. 5 is a longitudinal view, in cross-section, view similar to FIG. 2but showing tube and fitting according to a variation of the presentinvention;

FIG. 6 is a longitudinal view, in cross-section, of the tube and fittingof FIG. 5 as assembly is partly completed;

FIG. 7 is a longitudinal view, in cross-section, of the tube fitting ofFIG. 6 as assembly is completed;

FIG. 8 is a longitudinal view, in cross-section, view similar to FIG. 2but showing a tube and fitting according to another variation of thepresent invention;

FIG. 9 is a longitudinal view, in cross-section, of the tube and fittingof FIG. 8 as assembly is partly completed;

FIG. 10 is a longitudinal view, in cross-section, of the tube andfitting of FIG. 9 as assembly is completed;

FIG. 11 is a longitudinal view, in cross-section, view similar to FIG. 2but showing a tube and fitting according to yet another variation of thepresent invention;

FIG. 12 is a longitudinal view, in cross-section, of the tube andfitting of FIG. 11 as assembly is partly completed; and,

FIG. 13 is a longitudinal view, in cross-section, of the tube andfitting of FIG. 12 as assembly is completed.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1-4 illustrate a method for assembling a tube and fitting assembly20 according to the present invention. As best shown in FIG. 1, a rigidfitting 22 has a generally cylindrical forward portion 24 and agenerally cylindrical rear portion 26. The rear portion 26 of thefitting 22 may provide a wrench pad, such as a hexagonal surface. Theforward portion 24 is sized for extending into a malleable tube 28 andhas an outer diameter smaller than the outer diameter of the rearportion 26 to form a forward facing surface or longitudinal abutment 30.The abutment 30 is substantially perpendicular to the peripheral surfaceof the forward portion 24 of the fitting 22. Formed in the abutment 30is an annularly-shaped and forward facing groove or recess 32. Therecess 32 is sized and located for receiving a portion of the end of thetube 28 as the tube 28 is expanded during the assembly as described inmore detail hereafter. The recess 32 forms an annularly-shaped bottomsurface which is longitudinally recessed from the abutment 30.Preferably, a gasket 34 is provided at the rear end or "bottom". of therecess 32 as shown in FIGS. 1-4. The gasket 34 is preferably formed of amaterial which withstands high temperatures such as, for example,silicone. Alternatively, the gasket 34 could be an epoxy, sealant, orother suitable sealing member.

Provided on the forward portion 24 of the fitting 22 is acylindrically-shaped and radially facing recess or groove 36, that is, acylindrical surface 38 having a diameter smaller than the outer diameterof remainder of the forward portion 24. The groove 36 and cylindricalsurface 38 are contiguous with the abutment 30. Also provided on theforward portion 24 of the fitting is at least one barb 40. The fittingof the illustrated embodiment has two annular-shaped barbs 40, that is,barbs 40 which continuously extend around the periphery of the forwardportion 24 of fitting 22. The barbs 40 are preferably annular so that aseal may be obtained between the barbs 40 of the fitting 22 and the tube28. The barbs 40 are preferably located between the groove 36 and theforward end of the fitting 22. Each barb 40 has a sloping surface 42facing the forward end of the fitting 22 and has a locking surface 44facing away from the forward end of the fitting 22. The locking surface44 is substantially perpendicular to the peripheral surface of theforward portion 24 of the fitting 22.

As best shown in FIG. 1, the tube 28 is positioned over the forwardportion 24 of the fitting 22. The tube 28 may loosely telescope over theforward portion 24 of the fitting 22 or it may be a friction fit withthe barbs 40 actually scraping along the inside diameter of the tube 28.A portion of the end of the tube 28 is engaging the abutment 30 adjacentthe recess 32.

As best shown in FIG. 2, two jaws 46 are clamped on the tube 28 near theforward end of the fitting 22 and locked in position. It is noted thatwhile the illustrated embodiment utilizes two jaws 46, more jaws 46 maybe used. Each jaw 46 is provided with a radially inward extending noseprojection 48 which contacts the exterior surface of the tube 28. Thenose projections 48 are of limited axial length relative to the forwardportion 24 of the fitting 22. When the jaws 46 are clamped on the tube28 as shown in FIG. 2, the inward nose projections 48 of the jaws 46inwardly compress the tube 28 to make a substantially annular nose ring50. The nose ring 50 is annular except for the split between the jaws46. The jaws 46 also have a small forward extension 52 and a longerrearward extension 54. The forward extension 52 preferably has a smallclearance relative to the outside diameter of the tube 28. The rearwardextension 54 has essentially the same amount of clearance, relative tothe tube 28, for guiding the tube 28 between the jaws 46.

A longitudinal force is applied to start the assembly method byproviding relative movement between the jaws 46 and the fitting 22. Therelative movement can be obtained by longitudinally moving the jaws 46in a rearward direction relative to a stationary fitting 22, or bylongitudinally moving the fitting 22 in a forward direction relative tostationary jaws 46. In the illustrated embodiment, the longitudinalforce 56 is applied to a punch 58 brought into contact against therearward end of the fitting 22 while the jaws 46 are held stationary ina fixed position. Hence longitudinal relative movement is providedbetween the punch 58 and the jaws 46 and also between the fitting 22 andtelescoped tube 28 and the jaws 46.

When the assembly method is about half way completed, as best shown inFIG. 3, the jaws 46 remain closed and do not spring open as thelongitudinal relative movement is progressing. The metal material of thetube 28, which is malleable, forms a radially outward extending bulge 60ahead of the advancing nose ring 50. The bulge 60 may be radiallyrestrained by the forward extension 52 of the jaws 46. The relativelongitudinal movement also causes the malleable tube 28 to bulgeradially inward and to flow generally radially inward against thesloping surfaces 42 of the barbs 40 and against the cylindrical surface38.

As best shown in FIG. 4, the relative longitudinal movement is haltedwhen the nose projections 48 of the jaws 46 are adjacent the abutment 30of the fitting 22. The flowing metal caused by this relativelongitudinal movement causes the rearward end of the tube 28 to bejammed longitudinally against the abutment 30, to be contracted radiallyinward along the length of the fitting and against the cylindricalsurface 38 of the groove 36 and the sloping surfaces 42 of the barbs 40,and to be expanded longitudinally into the recess 32 against the gasket34. FIG. 4 illustrates the tube and fitting assembly 20 when completeexcept for removal of punch 58 and jaws 46. The material of the tubesubstantially fills both the groove 36 and the recess 32.

It has been found that a fluid-tight seal can be obtained at each of thebarbs 40, at the cylindrical surface 38, at the abutment 30, and at therecess 32. This seal is established by the relative longitudinalmovement without any radial inward compression of the jaws 46 as thejaws 46 move longitudinally relative to the punch 58. There is initialradially inward compression only at the nose ring 50. At least when thelongitudinal force 56 is removed and the jaws 46 are removed from thetube 28, any relaxation of the tube 28 is a radially inward relaxationrather than a radially outward relaxation as in the prior art. It hasbeen found that the tube 28 expands somewhat radially outward adjacentthe abutment 30, expands longitudinally rearward into the recess 32 andinto sealing engagement with the gasket 34,. and is contracted radiallyinward into sealing engagement with the cylindrical surface 38 of thegroove 36 due to the flow of metal of the malleable tube 28. It has beenfound that the seal of the tube and fitting assembly 20 will withstand1,000 PSI fluid pressure and in fact will make a tight seal up to atleast the bursting pressure of the tube 28 itself.

In tube and fitting assemblies 20 which have been tested and constructedin accordance with the invention, the barbs 40 have been annular barbsof about 0.015" to 0.030" larger radially than the cylindrical exteriorsurface of the forward portion 24 of the fitting 22. For example, if thetube 28 used is 3/8" outside diameter, the commercial standard toleranceis +/- 0.004" and the wall thickness is 0.032". Such a tube and fittingassembly 20 can withstand the 2,800 psi bursting pressure of the tube28. Even if a number of fittings 22 are manufactured and all mixedtogether, in one tote tray, this may put slight nicks in the barbs 40,but it has been found that these nicks are filled in by the flow of thetube metal by the time the fitting assembly is complete as shown in FIG.4. In any event, a fluid-tight seal is made at the cylindrical surface38, at the abutment 30, and at the recess 32 so that the totality of theseals prevents leakage up to the bursting pressure of the tube 28. Thisseal is maintained at high temperatures such as for example, up to atleast 500 degrees Fahrenheit. It is noted that the totality of the sealsalso permits the barbs 40 to be eliminated if desired. For 1/8" O.D.tube, the commercial standard tolerance is +/- 0.002" and the wallthickness is 0.028". In this case, the barbs 40 typically may be from0.005" to 0.015" in radial extent beyond the cylindrical exteriorsurface of the forward portion 24 of the fitting 22.

FIGS. 5-7, illustrate a tube and fitting assembly 62 which is avariation of the tube and fitting assembly 20 described above withrespect to FIGS. 1-4 wherein like references numbers are used for likestructure. The tube and fitting assembly 62 is the same except that atube 64, having a thinner wall thickness, relative to the tube 28, isutilized in conjunction with a sleeve 66. The sleeve 66 is necessarywhenever the tube 64 has a wall thickness that is too thin toconsistently form the seals as described above. The sleeve 66 has aninner diameter sized to receive the tube 64 therein and a length whichextends at least from the abutment 30 to the forward end of the fitting22. The sleeve 66 has a wall thickness adequate to form the seals inconjunction with the wall thickness of the tube 64. The sleeve 66 ispreferably formed of a malleable metal and is preferably formed of thesame material as the tube 64.

The assembly method is the same as described above except that both thetube 64 and the sleeve 66 are deformed by the nose projections 48 of thejaws 46 to form the seals. Although the sleeve 66 is only described indetail with regard to the tube and fitting assembly 62 of FIGS. 5-7, itis noted that the sleeve 66 can be utilized with each of the otherdescribed embodiments or variations of the present invention.

FIGS. 8-10 illustrate a tube and fitting assembly 68 which is anothervariation of the tube and fitting assembly 20 described above withrespect to FIGS. 1-4 wherein like references numbers are used for likestructure. The tube and fitting assembly 68 is the same as describedabove except that a recess 70 is provided which is deeper relative tothe previously described recess 32. The recess 70 is also sized andlocated for receiving the end of the tube 28 prior to deformation of thetube 28 by the jaws 46. As best shown in FIG. 8, the tube 28 isinitially positioned over the forward portion 24 of the fitting 22 withthe end of the tube 28 extending into the recess 70 and against thegasket 34.

The assembly method is the same as described above except that therelative longitudinal movement of the fitting 22 and the jaws 46 is nothalted until the nose projections 48 of the jaws 46 are generallyadjacent the gasket 32. As best shown in FIG. 10, the deformation of thefitting 22 caused by this additional relative longitudinal movementcauses the rear portion 26 of the fitting 22 is to be contractedradially inward against the tube 26. It has been found that the rearportion 26 of the fitting 22 contracts radially inward into sealingengagement with the tube 28. Although the relatively deep recess 70 andthe additional relative longitudinal movement are only described indetail with regard to the tube and fitting assembly 68 of FIGS. 8-10, itis noted that they can be utilized with each of the other describedembodiments or variations of the present invention.

FIGS. 11-13 illustrate a tube and fitting assembly 72 which is avariation of the tube and fitting assembly 68 described above withrespect to FIGS. 8-10 wherein like references numbers are used for likestructure. The tube and fitting assembly 72 is the same as describedabove except that at least one auxiliary sealing member 74, 76 isprovided between the fitting 22 and the tube 28. In the Illustratedembodiment a first auxiliary sealing member 74 is located between theouter surface of the tube 28 and the radially outward side of the recess70 and a second auxiliary sealing member 76 is located between the innersurface of the tube 28 and outer surface of the forward portion 24 ofthe fitting 22. Preferably, seats are formed in the rear portion 26 ofthe fitting 22 and the forward portion 24 of the fitting 22 for thefirst and second auxiliary sealing members 74, 76 respectively. Eachauxiliary sealing member 74, 76 is preferably an o-ring but couldalternatively be a flat gasket, epoxy, sealant, or other suitablesealing member. The sealing members 74, 76 are preferably formed of ahigh temperature material such as, for example, silicone.

The assembly method is the same as described above. As best shown inFIG. 13, the first auxiliary sealing member 74 is compressed whenrelative longitudinal movement causes the rear portion 26 of the fitting22 is to be contracted radially inward against the tube 26 and thesecond auxiliary sealing member 76 is compressed when the relativelongitudinal movement causes the tube 28 to be contracted radiallyinward against the forward 24 portion of the fitting 22. It has beenfound that the rear portion 26 of the fitting 22 and the tube 28 eachcontract radially inward to compress the auxiliary sealing members andform additional seals between the tube 28 and the fitting 22. Althoughthe auxiliary sealing members 74, 76 are only described with regard tothe tube and fitting assembly 72 of FIGS. 11-13, it is noted that theycan be utilized with each of the other described embodiments orvariations of the present invention.

Although particular embodiments of the invention have been described indetail, it will be understood that the invention is not limitedcorrespondingly in scope, but includes all changes and modificationscoming within the spirit and terms of the claims appended hereto.

What is claimed is:
 1. A method of assembling a malleable tube to afitting, the fitting having a first portion forming an external surface,a second portion radially larger than the first portion to form anabutment facing the first portion, and a recess formed within theabutment and facing the first portion, said method comprising the stepsof:placing the tube over the first portion of the fitting and theexternal surface; gripping the tube with jaws which have an inward noseprojection of a small axial extent at about the forward end of thefitting; longitudinally moving the fitting and the tube relative to thejaws until the nose projection is generally near the abutment after thestep of gripping the tube with the jaws; longitudinally compressing thetube ahead of the nose projection during the step of relativelongitudinal movement to deform the tube radially inward against thefitting; and extending a portion of the tube into the recess to form aseal between the tube and the fitting.
 2. The method as set forth inclaim 1, wherein the step of extending a portion of the tube into therecess includes expanding the tube longitudinally into the recess duringthe step of relative longitudinal movement.
 3. The method as set forthin claim 1, wherein the step of extending a portion of the tube into therecess includes inserting the tube longitudinally into the recess duringthe step of placing the tube over the first portion of the fitting. 4.The method as set forth in claim 1, wherein the step of longitudinallymoving the fitting and the tube relative to the jaws continues until thenose projection is generally near the bottom of the recess.
 5. Themethod as set forth in claim 1, further comprising the step of placing asealing member in the recess prior to the step of extending a portion ofthe tube into the recess.
 6. The method as set forth in claim 1, furthercomprising the step of placing a malleable sleeve over at least theportion of the tube over the first portion of the fitting.
 7. The methodas set forth in claim 6, wherein said at least one auxiliary seal isplaced between an exterior surface of the tube and an outer surface ofthe recess.
 8. The method as set forth in claim 6, wherein said at leastone auxiliary seal is placed between the an interior surface of the tubeand the exterior surface of the first portion of the fitting.
 9. Themethod as set forth in claim 1, further comprising the step of placingat least one auxiliary seal member between the fitting and the tubeprior to the step of gripping the tube with the jaws.